Switching regulators used in portable applications usually have two modes, a normal mode and a mode for light load conditions. In the normal mode the output stage of the regulator is always switching by pulse width modulation (PWM) or equivalent. The normal mode can deliver high output current and maximize performance. In the light load mode the output of the switching regulator is switching intermittently reducing power consumption to improve power conversion efficiency. An automatic mode change function improves the usability of the switching regulator, wherein output current less than a given threshold automatically places the regulator into a light load mode to save power consumption. If the output current is above the given threshold, the regulator changes to a normal mode for maximum current and performance.
DC to DC converters have the capability to change output voltage dynamically to improve system efficiency by using dynamic voltage control (DVC) or dynamic voltage scaling (DVS). The most popular application of either the DVC or the DVS is in powering an application processor or an RF amplifier in a portable device, wherein a regulator supplies high voltage to maximize performance or the regulator is operated in a low power mode where the regulator supplies a lower voltage and operating at a lower power consumption state.
Some switching regulators have both the automatic mode change and the DVS/DVC capability. A certain delay is required to accommodate current sensing thus causing automatic mode change based on output current to take time, thus changing the mode in advance maximizes the response of the regulator to a change output mode or condition. To achieve a mode change in advance, some converters have an output voltage threshold as well as an output current threshold and when the output voltage target is low, the converter goes to light load quickly.
US 2012/0007661 (Hur) is directed to an apparatus and method for determining dynamic voltage scaling mode and apparatus and a method for pumping voltage using the same. In US 2012/0299564 (Howes et al.) a low drop-out voltage regulator is directed to minimizing power consumption of a load circuit by dynamically adjusting the output voltage. U.S. Pat. No. 8,238,868 B1 (Duan et al.) is directed to a dynamic voltage scaling system for packet based data communications transceiver including a constant and variable voltage supply and a voltage control unit. U.S. Pat. No. 8,181,051 B2 (Barth) is directed to an electronic apparatus and method for conserving energy comprising an energy-conservation module to control the use of one or more energy-saving mechanisms. In U.S. Pat. No. 8,135,966 B2 (Rozen et al.) a device and method of power management is directed to providing at least one clock signal and one supply voltage in response to the long term and the short term supply parameters. U.S. Pat. No. 8,112,644 B2 (Huang et al.) is directed to a dynamic voltage scheduling method that executes at least one of several steps for sporadic and hard real time tasks with resource sharing. U.S. Pat. No. 8,009,090 (Vishin et al.) is directed to a system and method to dynamically vary supply voltages and clock frequency to perform dynamic voltage scaling for a GPS receiver.
In each application and system design the automatic mode change requirements and voltage threshold vary from user to user causing the regulator design to be modified frequently and adding to product cost. A scheme is needed that is flexible with few parameters and can be used in a wide variety of applications without design modifications.